Author Topic: Ended Up with Two CB750's  (Read 3957 times)

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Offline DennyK

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Ended Up with Two CB750's
« on: February 28, 2014, 03:50:21 PM »
This is my first contribution to the Forum but I have been reading and searching the Forum for nearly a year.  Last year I sold my old Royal Enfield Bullet and discovered that what I really liked doing was working on it; if you ever owned a Bullet you will know what I mean, however, I started watch the Cafe Racer series on TV and thought building up an old bike would be a lot of fun. 

Last spring I went to a local vintage bike show and met a guy that had a 1971 CB750 basket case for sale cheap.  This bike had a prior life as a chopper; it has a Harley wheel on back, ape hangers, a sissy bar and a seized engine.  My son and I decided this would be a great bike to learn on.  So we started taking it apart and had some fun doing that.  The bike has some nice parts and pieces; you just have to know where to look. 

In the fall I ran into a 1974 barn find with an engine that turned over, low mileage and was able to get if for a good deal.  The PO told me that the bike has not run for over 8 years.  It was parked on the kickstand and the front caliper was frozen to the disc.   Luckily I learned a thing or two in working on the '71 and we were able to take the caliber apart and get the bike loaded.

This past winter I cleaned up the carbs a bit, the bank with #3 & #4 was clogged and I did a lot of research on trying to get the '74 to actually start.  I figured if I could get it to run then we would get serious about moving ahead.  I changed the oil in the bike, replaced oil filter, got a new battery, did a quick vinegar wash on the tank and mixed some Seafoam in with fresh fuel, and this past weekend we had success.  There was a lot of smoke from burning dust, old oil on the engine, and the carbs leaked quite a bit from above the bowls.  We did two runs, one for about 5 minutes and one for about 10 minutes and then we let her cool down and removed the tank and salvaged the fuel for the lawnmower. 

So now the fun begins. The carbs are back off the bike and are getting an ultrasonic cleaning.  I need to get my carb kits ordered and we need to redo the front brake system, and of course the brake pad is stuck in the caliper.  I am really thinking the thing to do is order a new after market master cylinder and get a new after market caliper.  The brake lines are old and the metal pipe is pretty shot as well.  The head light smoked a bit, so that is on the list.    We may decide to get this bike in running condition and put a few miles on it before starting in on the major project.  I just wish I had a larger garage; I need to find a place for the '71 and all those good bits and pieces.  Anyone need a 1970's sissy bar?

I would love to include pictures but have spent 45 minutes trying...so if someone can tell me the steps to do that, I will post some shots of the two bikes

Cheers

Offline 70CB750

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Re: Ended Up with Two CB750's
« Reply #1 on: February 28, 2014, 03:55:10 PM »
Welcome!

You need 5 posts to be allowed to post pictures.
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Offline MoMo

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Re: Ended Up with Two CB750's
« Reply #2 on: February 28, 2014, 04:18:36 PM »
Welcome,  wish my son was interested in motorcycles-seems like a good bonding  scenario...Larry

Offline DennyK

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Re: Ended Up with Two CB750's
« Reply #3 on: February 28, 2014, 04:43:56 PM »
Thanks for letting me know the 5 post rule regarding pictures.  The bikes have been a nice bonding experience for Sonny and me. We are also explaining to his son (11 years old) how a gas engine works while we were cranking the bike

Offline jpfrk2001

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Re: Ended Up with Two CB750's
« Reply #4 on: February 28, 2014, 05:10:17 PM »
You can also use photobucket. Start a account, its free, no hidden fees. And lately, the site is more user friendly then 7 years ago.
I do tasks the most difficult way. My life is interesting.

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Offline DennyK

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Re: Ended Up with Two CB750's
« Reply #5 on: March 01, 2014, 04:09:12 PM »
Thanks for the tip on the photos.  I am going for the five posts.  Got my carbs back from the ultrasonic cleaners today.  They look pretty darn good and the final cleanup should be pretty easy.  The guy doing the cleaning noticed that one of the set screws was cross threaded.  We messed with it a bit, but may need to look into a little machine shop work.  Also one of the throttle rod caps has a broken bushing.  The part shows up as "discontinued".  Any good solutions for that?  I may need to rob one from the '71.

Offline DennyK

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Re: Ended Up with Two CB750's
« Reply #6 on: March 20, 2014, 09:56:41 PM »
I wanted to report that I was able to finally get the stuck brake pad and piston out of the caliper on my 74 CB750 using the grease gun approach.  The trick was finding the right grease cert and I was able to get a couple through Fastenal.  Finding a 10 mm 1.25 twist is not easy.  Once installed I simply pumped the caliper full of grease and the parts slowly came out.  All the crud and rust would have made getting this apart with air pressure pretty dicey, I think.  Thanks to all the contributors to this Forum regarding stuck brake parts.  There is also a YouTube video of someone using this technique.

Offline mrbreeze

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Re: Ended Up with Two CB750's
« Reply #7 on: March 20, 2014, 11:14:54 PM »
Looks like you only need 1 more post to put up your pictures.Just type in anything and then you can show us what you have.
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Offline DennyK

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Re: Ended Up with Two CB750's
« Reply #8 on: March 21, 2014, 06:02:37 AM »
Okay, thanks for the tip.  This will make 5 posts.

Offline DennyK

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Re: Ended Up with Two CB750's - Not yet with Pictures
« Reply #9 on: March 21, 2014, 02:21:10 PM »
Well I am trying to post some pics but have not figured it out.  I use the insert picture button, but I can't copy anything in between.  Sorry for being such a rookie.


Offline MoMo

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Re: Ended Up with Two CB750's
« Reply #10 on: March 21, 2014, 02:30:14 PM »
Well I am trying to post some pics but have not figured it out.  I use the insert picture button, but I can't copy anything in between.  Sorry for being such a rookie.





to use that you need to upload from something like Photobucket,  to add from your computer click the attachments and other options below the message ...Larry

Offline DennyK

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Re: Ended Up with Two CB750's - Pictures Included
« Reply #11 on: March 21, 2014, 02:46:33 PM »
Here are the two bikes I acquired last year.  We are going to figure out how to hold on to the 1971.  There are some great parts on it and actually I think some things are in better shape than the 1974.  We got the '74 running a couple of weeks ago and I now need to rebuild the carbs and figure out the front brake system.  With the brake pad and piston out, rebuilding is an option, but I am seriously considering after market parts for the front brake.  Any suggestions would be appreciated.

Thanks MoMo for the direction on posting using the attachments.
« Last Edit: March 22, 2014, 11:30:30 AM by DennyK »

Offline gto_ron

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Re: Ended Up with Two CB750's
« Reply #12 on: March 22, 2014, 05:48:21 PM »
Hey Denny

I hope you enjoy the project, are your 4-into-4 exhausts going to be useable? 
Ron


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why yes, I am old-school, so what? 

These are the good old days.

Offline DennyK

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Re: Ended Up with Two CB750's
« Reply #13 on: March 23, 2014, 09:17:53 AM »
No the old exhaust system on the '71 was totally rusted out.  I did save the trim pieces from the pipes, they might be of value to someone and I am generally hard pressed to throw much away, besides taking something apart is lots of fun.  One of the flanges is seized in the '71's engine.  The pipes on the '74 have to be after market 2 into 1.  The pipes are in pretty good shape, but there's a lot of rust spots on the silencers.  Off on a feral pig hunt and some fishing down south, so all work is on hold. 

Offline Stev-o

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Re: Ended Up with Two CB750's
« Reply #14 on: March 23, 2014, 09:34:01 AM »

With the brake pad and piston out, rebuilding is an option, but I am seriously considering after market parts for the front brake.  Any suggestions would be appreciated.




First off, welcome.  On the caliper, getting the piston out is the battle.  Were you able to loosen the bleeder screw?
So, what do you think needs replacement?
'74 "Big Bang" Honda 750K [836].....'76 Honda 550F.....K3 Park Racer!......and a Bomber!............plus plus plus.........

Offline DennyK

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Re: Ended Up with Two CB750's
« Reply #15 on: March 23, 2014, 09:57:55 AM »
I did finally get the piston out using the grease gun approach.  Took a lot of effort to get the right cert but once I had that the job was easy.  The other challenge was getting the snap ring out of the master cylinder, but I did manage without the right snap ring pliers. 

As I look at the front brake system, the master cylinder needs to be rebuilt and I would probably invest in the right pliers to do the job.  I plan to buy new brake lines and the brake pipe needs to be replaced as well.  The bleeder comes out fine and held pressure when I applied the grease.  The piston as a lot of pits in it so I think that needs to be replaced too.  As I compare costs to do the rebuilds on the caliper and master cylinder including the pliers I wonder if buying a new after master cylinder and caliper might be the way to go.  There are a couple of sources for the MC and one for the caliper.  The caliper does not have a “stock” look, but still looks pretty nice.  Our disc has some surface rust on it and maybe we should take it to a shop to have it refaced. 

Thanks so much for responding.

Offline Stev-o

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Re: Ended Up with Two CB750's
« Reply #16 on: March 23, 2014, 10:11:08 AM »
Not worth rebuilding the master cyl, and they can be a real pain, as you are finding out.

DSS sells a nice aftermarket one for $45, a no brainer in my book, if not doing an 100 point restoration. 

http://www.davidsilverspares.com/CB750K4-FOUR-1974-USA/part_123914/

They also sell the caliper piston for $28.

Good luck. 
'74 "Big Bang" Honda 750K [836].....'76 Honda 550F.....K3 Park Racer!......and a Bomber!............plus plus plus.........

Offline DennyK

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Re: Ended Up with Two CB750's
« Reply #17 on: March 23, 2014, 11:06:50 AM »
Thanks for the link.  I have not yet found this source and like what I see.

Cheers!

Offline DennyK

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Re: Ended Up with Two CB750's
« Reply #18 on: September 05, 2014, 03:47:41 PM »
Folks,
I have made some good progress with our 1974 CB750.  It is now roadworthy and we are doing some shake down rides to discover how solid everything is; finally got plates and insurance.  Original miles are under 14,000.  I believe we have simply done the basics by rebuilding the carbs, redoing the front brake, and a lot of general cleanup and tune up.

I am not traveling too far from the barn at this time, but I am noticing that something is taking down my battery.  I connect the battery to a tender, so it is always "green" when we get started.  The flasher is weak and using the starter really seems to run things down.  I read some info about replacing the flasher, but I need to find the source of the issue.  I have done some work on the connectors simply cleaning and reconnecting.

Our plan is to keep improving the bike and keeping it close to stock.  It sure is fun to ride...haven't been in the saddle since I sold my RE Bullet a couple of years ago. 

Offline MoMo

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Re: Ended Up with Two CB750's
« Reply #19 on: September 05, 2014, 05:38:03 PM »
Have you checked to make sure the system is charging? ....Larry

Offline DennyK

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Re: Ended Up with Two CB750's
« Reply #20 on: September 05, 2014, 09:50:24 PM »
No, I have not. I was going to research that in the shop manual tomorrow.  Any advice regarding what to check. I am old but still a novice at this.  Thanks

Offline Restoration Fan

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Re: Ended Up with Two CB750's
« Reply #21 on: September 05, 2014, 10:58:19 PM »
No, I have not. I was going to research that in the shop manual tomorrow.  Any advice regarding what to check. I am old but still a novice at this.  Thanks

I'm just learning on these things as well, but from what I understand it may be your rectifier.
Ron

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Offline MoMo

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Re: Ended Up with Two CB750's
« Reply #22 on: September 06, 2014, 02:12:30 AM »
No, I have not. I was going to research that in the shop manual tomorrow.  Any advice regarding what to check. I am old but still a novice at this.  Thanks

I'm just learning on these things as well, but from what I understand it may be your rectifier.




That is the most common charging malfunction.  To  check charging, put a voltmeter across battery terminals-voltage should rise over 14v above 3000 rpm.   If low, then use the manual to troubleshoot, most likely culprit will be the rectifier...Larry

Offline calj737

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Re: Ended Up with Two CB750's
« Reply #23 on: September 06, 2014, 04:33:29 AM »
No, I have not. I was going to research that in the shop manual tomorrow.  Any advice regarding what to check. I am old but still a novice at this.  Thanks

Use this: http://www.electrosport.com/media/pdf/fault-finding-diagram.pdf
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Offline DennyK

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Re: Ended Up with Two CB750's
« Reply #24 on: September 08, 2014, 09:23:58 PM »
Guys,
Thanks for all the comments, this is why I really like this Forum.  I did some research, read the shop manual and downloaded info from Oregon Motorcycle on testing the bike's electrical and charging system.  I also sent an email to Oregon Motorcycle describing my issues and within an hour I had a reply back with some additional advice.  I am going to replace the old rectifier and voltage regulator, I just need to get the parts ordered from Oregon.  Plan to keep testing the system just to learn more and besides this is fun!